Replace unnecessary format macro with `to_string()`

Checks for the use of format!("string literal with no argument") and format!("{}", foo) where foo is a string.

Apply with the Grit CLI

grit apply no_useless_format

Replaces a string literal with no argument

BEFORE

let hi = format!("hello");

AFTER

let hi = "hello".to_string();

BEFORE

let greeting = "hello";
let hi = format!("{}", greeting);

AFTER

let greeting = "hello";
let hi = greeting.to_string();

RUST

let hi = format!("hello {}", "world");
let another = format!("{:?}", strawberry);